Some semiconductor devices require the use of fuses. Two common types of fuses are the laser fuse and electrical fuse or efuse. Laser fuses are programmed, broken down or “blown” by applying a focused laser beam at the fuse, while electrical fuses are programmed, broken down or “blown” by passing a suitable electrical current through the electrical fuse. Such fuses are used in semiconductor devices for rerouting signal paths, enabling redundancy, providing programming functions, codes in logic chips and encryption, etc.
Electrical fuses are often preferred over laser fuses as they have a significantly lower production cost than laser fuses and may be programmed once the integrated circuit containing the fuse is already packaged. In use, a predetermined programming voltage is required to program or blow such electrical fuses. Generally, it is desirable for the predetermined programming voltage to be compatible with the voltage(s) required by the remainder the integrated circuitry. However, as the performance of integrated circuits increase and circuit sizes decrease, the voltages required by the remainder of the circuitry have lowered significantly. For example, emerging advanced technologies, e.g., <100 nm, require a Vcc significantly lower than 3.3v. Moreover, the boom in cellular telephones and handheld computing devices has provided the impetus for even lower power integrated circuits.
Currently, however, voltages of at least 3.3v are required to program or blow an electrical fuse. As mentioned above, this voltage is significantly higher than the voltage required by certain integrated circuitry, and therefore requires special design attention. For example, current integrated circuits that include electrical fuses may require additional power sources and circuit routing for the electrical fuses. To maintain high fuse blow power, blowing transistor sizes increase at lower voltages to increase current, or charge pumps are needed to boost voltage. Accordingly, it would be highly desirable to provide an electrical fuse that is capable of being programmed or blown at lower voltages than those currently employed.
Furthermore, to reduce costs and increase manufacturing efficiency it is desirable that the electrical fuses included in integrated circuits be fabricated from the same materials and using the same thin-film processes as the remainder of the integrated circuit. It is also desirable that the electrical fuses have as small a size as possible to minimize the overall size of the integrated circuit.
In light of the above, it would be highly desirable to provide an electrical fuse that is capable of being programmed at lower voltages and is made from the same materials and using the same processes used to make the remainder of the integrated circuit.